(a) Field of the Invention
The present invention relates to an antenna for mobile communication. More specifically, the present invention relates to a wide band antenna for mobile communication for providing wide band frequency features and enabling a user to easily distinguish normal radiation states of the antenna.
(b) Description of the Related Art
Various wireless communication services have become available in fields such as cellular phones and personal communication services (PCS), and the next generation mobile communication system, the IMT-2000 service, will be issued in the near future. Accordingly, more techniques for minimizing and reducing the weight of terminals or base station communication devices have been required.
Recent developments of additional functions such as wireless data communications mean that the conventional communication services have been lifted to a higher level from mere voice-centered communications. To use the plural communication services, plural antennas for the respective services must be installed. Therefore, mobile communication service providers build repeaters and small patch antennas each connected to the repeater in buildings so as to enable the mobile communication services in tall buildings or basements.
For example, cellular mobile communications of about 800 MHz frequency band and PCS communications of 1,800 MHz frequency band have been commercialized, and since these two communication methods use different frequency bands, the mobile communication service providers separately install respective cellular phone patch antennas and PCS patch antennas, and they will have to install IMT-2000 patch antennas in the near future.
FIG. 1 shows general mobile communication patch antennas.
As shown, the general mobile communication patch antennas are categorized as follows according to feeding methods: a microstrip feeder type patch antenna, a coaxial cable feeder type patch antenna and a slot coupling feeder type patch antenna.
The general mobile communication patch antenna comprises a dielectric substrate 10, a ground surface 13 and a metallic radiation element 11. FIG. 2 shows frequency characteristics of this patch antenna.
As the gap between the radiation element 11 and the ground surface 13 becomes greater and the dielectric constant of the dielectric substrate 10 becomes that of the air, effectiveness and bandwidth of the patch antenna are increased.
However, the general patch antenna shown in FIG. 1 has a restriction in the case of expanding the frequency bands, and when the dielectric substrate 10 is designed to have low dielectric constant, the design cost is increased because a thick and low dielectric constant substrate 10 generates high-order surface waves.
As described above, because of the bandwidth restriction caused by its structure, the general patch antenna cannot be a common use antenna for supporting various mobile communication services such as cellular phones, PCS and IMT-2000. Hence, respective antennas corresponding to the various services must be separately installed, and accordingly, this installation spoils the beauty of the interiors of buildings and generates excessive installation and maintenance costs.
Since a repeater installed in a building adopts a low power output method, a plurality of patch antennas must be installed on each floor of a building. In this case, a user cannot determine whether signal power is radiated from the installed patch antennas in the rated manner. In other words, the user cannot distinguish with the naked eye whether the patch antennas are normally operating. To check their operating states, the user must either check receipt power while the user is near the antenna using a terminal or measure the same using a spectrum analyzer, thereby causing inconvenience.